Vibration damping means are generally utilized for a friction clutch in the drive line of an automotive vehicle between the engine and the manually operated transmission to overcome objectionable rattle and vibration when the clutch is engaged and provides a torsional coupling between the engine and transmission. A conventional vibration damper and clutch assembly includes a hub having an internally splined barrel receiving the externally splined end of the transmission input shaft and an integral radial flange, a clutch plate journalled on the hub and carrying the friction facings at its periphery, a spring retainer plate journalled on the hub on the opposite side of the flange from the clutch plate and connected thereto by stop pins extending through peripheral notches in the hub flange, and damper springs which are located within axially aligned sets of spring windows formed in the clutch plate, hub flange and spring retainer plate.
The above described clutch and vibration damper assembly provides for a substantially constant rate of energy dissipation, and friction washers may be sandwiched between the plates and hub flange to provide for an additional friction damping action to supplement the resilient damping action of the springs. However, this damper assembly has proved to be inadequate where specialized problems occur at idle conditions or under engine full load. One specific problem resides in transmission gear rattle in the neutral position with the clutch engaged at idle rpm. The gear rattle is caused by motor impulses urging the gears of the transmission to oscillate through their tooth backlash space; the impacting of the gear teeth producing the objectionable rattle.
The present invention resides in a multi-stage vibration damper assembly which will overcome the problem of objectionable gear rattle at idle rpm and also cushion the torque transference between damping stages without impacting the damper parts.